The present invention relates to an inspection unit to be employed for inspecting an electronic component to be inspected such as a semiconductor integrated circuit, and more particularly, to a connecting structure between a contact probe for grounding and a metal block in the inspection unit which has the contact probe for grounding.
In order to inspect an electronic component to be inspected such as a semiconductor integrated circuit, there has been employed an inspection unit (socket) having a number of contact probes which are brought into contact with electrodes of the electronic component to be inspected. In the inspection unit dealing with high frequency, contact probes for high frequency signal, contact probes for power supply, and contact probes for grounding (GND) are arranged passing through respective through holes in a metal block, for the purpose of preventing influence of noises.
An example of the inspection unit of this type is disclosed in JP-A-2006-98375.
FIGS. 11(A) and 11(B) show a part where a contact probe for grounding is mounted in an inspection unit of the related art, and FIG. 11(C) shows a ground tube which connects the contact probe for grounding to a metal block.
As shown in FIGS. 11(A) and 11(B), a contact probe 1 for grounding is an electrically conductive structure including a conductive tube 2 in a cylindrical shape, and conductive plungers 3, 4 which are urged so as to be projected from the conductive tube 2 by a spring incorporated therein, and is so arranged as to pass through a through hole 11 in a metal block 10. The contact probe 1 for grounding is coaxially held with respect to an inner peripheral face of the through hole 11, by means of retainers (fixing means of insulating substance) 12, 13 which are fixed to upper and lower faces of the metal block 10.
Connection between the contact probe for grounding and the metal block is conducted by using a ground tube 20, as shown in FIG. 11(C). The ground tube 20 is produced by folding a metal plate into a tubular shape. One end of the ground tube 20 is folded so as to have a slightly smaller inner diameter than an outer diameter of the probe 1 for grounding so that the ground tube 20 can be contacted with an outer peripheral face of the probe 1, and the other end is enlarged so that the ground tube 20 can be contacted with the inner peripheral face of the through hole 11. This ground tube 20 is provided in a gap between the probe 1 and the metal block 10 thereby to achieve electrical connection between them.
Although not shown in the drawings, the metal block 10 has a number of through holes. In other through holes which are not shown, the contact probes for high frequency signal and contact probes for power supply are arranged coaxially with respect to the metal block 10 in an isolated manner.
An upper face of the retainer 12 which is fixed to the upper face of the metal block 10 is a mounting face on which an electronic component to be inspected is to be mounted. When the electronic component to be inspected is positioned and mounted on this mounting face, a distal end (an upper end) of the contact probe 1 for grounding is brought into contact with an electrode pad for grounding of the electronic component to be inspected. Moreover, the contact probe for high frequency signal and the contact probe for power supply are respectively brought into contact with an electrode pad for high frequency signal and an electrode pad for power supply of the electronic component to be inspected.
In case where the ground tube of the related art which is formed by folding a metal plate into a tubular shape is used, as described above, there are such problems as described below.
(1) Intervals between the electrodes tend to become smaller, as the electronic component to be inspected becomes more and more compact and high integrated. For this reason, the contact probe which is smaller in outer diameter has been requested. Different from the tube of the probe, the ground tube in the related art is produced by folding the metal plate which has been stamped out, and hence, as the diameter becomes smaller, it becomes more difficult to work the metal plate into the tubular shape. Therefore, it becomes difficult to apply the ground tube in the related art to the contact probe for grounding which has the smaller diameter.(2) The ground tube in the related art is formed by folding the metal plate into the tubular shape, and further, into such a shape that its diameter at the other side is enlarged. Therefore, working cost is high.(3) The ground tube had better be long, as shown in FIGS. 11(A), 11(B), 11(C), for enabling adequate contact pressure (pressure of contact) against the metal block and the contact probe for grounding to be easily obtained. However, a contact position with respect to the metal block is at an opposite side to a contact position with respect to the contact probe for grounding. As the results, an electrical path from the contact probe for grounding to the metal block grows longer by a length of the ground tube. This structure is unfavorable from a view point of high frequency performance, because in order to obtain favorable high frequency performance, grounding has better be attained at a position close to the electronic component to be inspected. Even though the length of the ground tube is reduced considering the high frequency performance, there occurs such a problem that it becomes difficult to work the ground tube (it becomes difficult to adjust the contact pressure).(4) When the ground tube in the related art is incorporated into the through hole in the metal block together with the contact probe for grounding, a step for adjusting the inner diameter and so on of the ground tube by means of a pin gauge or the like is required.